1. Field of the Invention
The present invention generally relates to a photographic lens mount, and more specifically a barrel for a variable focal length lens.
The present invention applies, in particular, to miniaturized objectives of photographic devices or cameras such as those used in photographic devices associated with cellular phones, in which an image is formed on a semiconductor chip comprising an optical sensor network.
2. Description of the Related Art
It is often desired to associate an objective, having a variable focal length, with an image sensor, to enable focusing or zoom effect. Conventionally, this is performed by arranging one or several lenses in a barrel comprising parts mobile with respect to one another, generally, in connection with a rotation of barrel elements which causes a relative shifting between the lenses forming the objective.
Electrically-controlled variable focal length optical systems having no mobile parts, such as electrowetting lenses, have been developed. Such lenses have a focal length which varies according to an applied voltage. Lenses with a variable focal length are being developed, which, as seen from the outside, are in the same housing type as button batteries. Such electrowetting lenses are for example available from VARIOPTIC Company.
An example of button-battery type variable focal length lens housing is illustrated in FIGS. 1A to 1C, in which FIG. 1A is a top view, FIG. 1B shows the contour of a transverse cross-section, and FIG. 1C is a bottom view. The central portion of the structure corresponds to the optical portion and comprises an upper transparent plate 1 and a lower transparent plate 2 between which is arranged the optical system with a variable focal length. Upper peripheral portion 3, lateral portion 5, and lower end periphery 6 correspond to a first metal surface forming a first electrode. Intermediary portion 8 between the external peripheral portion and central plate 2 on the lower surface side corresponds to a second metal surface forming a second electrode. Often, upper and lower portions 4 and 8 are not planar and comprise respective bumps 11 and 12. On the lower surface side, an insulating crown 14 separating the two electrodes can be seen.